The polyhydroxy alkaloid glycosidase inhibitors swainsonine [1] and calystegine B2 [6] have been identified as constituents of the seeds of the Australian plant Ipomoea sp. Q6 [aff. calobra] (Weir vine) by gas chromatography-mass spectrometry and by their biological activity as inhibitors of specific glycosidases. This plant, which is known only from a small area of southern Queensland, has been reported to produce a neurological disorder when consumed by livestock. The extract of the seeds showed inhibition of alpha-mannosidase, beta-glucosidase, and alpha-galactosidase, consistent with the presence of 1 and alkaloids of the calystegine class. Histological examination of brain tissue from field cases of sheep and cattle poisoned by Weir vine showed lesions similar to those observed in animals poisoned by the swainsonine-containing poison peas (Swainsona spp.) of Australia and locoweeds (Astragalus and Oxytropis spp.) of North America. These results indicate that Weir vine poisoning is an additional manifestation of the induced lysosomal storage disease, mannosidosis, possibly exacerbated by inhibition of the enzymes beta-glucosidase and alpha-galactosidase by calystegine B2. This is the first reported example of a single plant species capable of producing structurally distinct glycosidase inhibitors, namely, alkaloids of the indolizidine and nortropane classes.

Crotalaria species containing hepatotoxic pyrrolizidine alkaloids grow widely in pastures in northern Australia and have sporadically poisoned grazing livestock. The diverse Crotalaria taxa present in these pastures include varieties, subspecies, and chemotypes not previously chemically examined. This paper reports the pyrrolizidine alkaloid composition and content of 24 Crotalaria taxa from this region and assesses the risk of poisoning in livestock consuming them. Alkaloids present in C. goreensis , C. aridicola subsp. densifolia, and C. medicaginea var. neglecta lack the esterified 1,2-unsaturated functionality required for pyrrole adduct formation, and these taxa are not hepatotoxic. Taxa with high levels of hepatotoxic alkaloids, abundance, and biomass pose the greatest risk to livestock health, particularly C. novae-hollandiae subsp. novae-hollandiae, C. ramosissima , C. retusa var. retusa, and C. crispata . Other species containing moderate alkaloid levels, C. spectabilis and C. mitchellii , also pose significant risk when locally abundant.

Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculentoside, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum ) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.

Cardiac glycoside poisoning was produced in calves given (in descending order of toxicity) flower heads of the hybrid Bryophyllum (Kalanchoe) daigremontianum x B. tubiflorum, of B. pinnatum, of B. tubiflorum (from previous work), whole plant of B. fedtschenkoi, flower heads of B. daigremontianum and whole plant of B. proliferum. For each plant (except B. tubiflorum), 2 calves were each given a single dose of 20 g wet weight per kg bodyweight. By using high performance liquid chromatography, the bufadienolides (cardiac glycosides) bryotoxin A, B and C were detected and assayed in the flower heads and leaf plus stem of B. tubiflorum and in the roots of B. tubiflorum, the hybrid and B. pinnatum. Only bryotoxins B and C were detected and assayed in the flower heads and leaf plus stem of the hybrid, B. daigremontianum and B. pinnatum. No bryotoxins were detected in B. fedtschenkoi. Bryotoxin A and a mixture of bryotoxins B and C from B. tubiflorum flowers were used as standards in the chromatographic assay. Comparing the results of the calf toxicity experiment with the amounts of bufadienolide measured in the plants suggests that bryotoxins A, B and C probably account for the observed disease, but that B. pinnatum and B. fedtschenkoi contain at least one other cardiac glycoside.

Three ponies continuously grazed a pasture containing an estimated 24% Indigofera spicata (wet weight basis) for 4-6 weeks in April and May 2004. They developed ataxia, paresis, depression, muscle fasciculations, dysphagia, ptyalism and halitosis. Two also developed corneal opacity. One pony recovered with supportive treatment, but the other two were euthanased and necropsied. Neuropathology was not present in either case, but both livers had periacinar and periportal lymphocytic infiltrations and hydropic degeneration of mid-zonal hepatocytes, with mild to moderate periacinar necrosis also evident in one. The I. spicata contained 2.66 mg 3-nitropropionic acid (3-NPA)/g dry matter and 1.5 mg indospicine/g dry matter. Indospicine, but not 3-NPA, was detected in serum from both of the euthanased ponies and indospicine was detected in heart, liver and muscle from the one pony in which this assay was performed. The clinical syndrome closely resembled 'Birdsville horse disease' caused by I. linnaei and was similar to that reported in horses poisoned by the closely related species I. hendecaphylla and to 3-NPA poisoning of other animals, including humans. 3-NPA is thought to cause this neurological syndrome. To our knowledge, this is the first authenticated report of I. spicata poisoning in grazing animals. We also report here the first published evidence that 3-NPA and indospicine exist in naturalised I. spicata in Australia and of the formation of indospicine residues in tissues of animals grazing paddocks infested with I. spicata.